Autonomic Physiology Flashcards
(46 cards)
Function of the autonomic nervous system
To control things you dont want to think about:
* Smooth muscle: blood vessels/airways/bladder/eye/gut/sex organs
* Cardiac muscle
* Glands
How can we divide the PNS
Afferent division
Efferent division:
* Autonomic NS (sympathetic, parasympathetic, enteric NS)
* Somatic NS - voluntary (muscles)
Describe the somatic nervous system in terms of nerves/recepotors
(briefly)
Nerve emerging from ventral root and sysnapeses onto skeletal muscle (n-m junction)
see sheet
Describe the autonomic nervous system in terms of nerves/recepotors
(briefly)
Pre-ganglionic fibre (small myelinated) —> synapse and ganglion —> post-ganglionic fibbre (unmyelinated) —> synaps onto smooth/cardiac muscle, gands, GI neurons
see sheet
Breifly describe the main features of synapses in the somatic nervous system
- Specialised NMJ
- Ionotropic (nicotinic cholonergic) receptors which act as monovalent cation channels
- Graded potential called end plate potential which always ecites target
Breifly describe the main features of synapses in the autonomic nervous system
- Less specialised junction
- Metabotropic receptors - G-protein coupled
- Can be exitory or inhibitory
- Neurotransmitter released into ISF until it finds receptors, therfore 1 postganglionic fiber innervates a large tissue area
2 main divisions of the autonomic nervous system
Give key rhymes for each
- Sympathetic - fight or flight
- Parasympathetic rest and digest
Outflow of sympathetic division of NS
Thoratic (T1-T12) region of spinal cord and first 2 lumbar levels (L1-L2) - thoracolumbar outflow
Describe ganglia/fibres of sympathetic NS
Very short pre-ganglionic fibres (ganglia close to spinal cord). Most found in sympathetic chain, aka the paravertebral ganglia
And then we’ve got some in these other ganglia called the collateral (or prevertebral) ganglia.
After the synapse, there are very long post-ganglionic fibres that go all the way up to their targets.
Ganglia lie close to spina cord
see diagram
Outflow of parasympathetic division of (autonomic) NS and what does it supply
Cranial (3,7,9,10) and sacral (S2-S4) regions of spinal cord - craniosacral
Cranial nerves supplies head/eyes/salivary glands but vagus nerve goes on an adventure (e.g. lungs/hear/liver/intestine…)!
Describe ganglia/fibres of parasympathetic NS
Very long pre-ganglionic fibres and very short post-ganglionic fibres which lie within the target/very close to it.
Ganglia lie close to/within target
Neurotransmitters and receptors of somatic nervous system
Only has n-m junctions so:
* Neurotranmitter: acetylcholine
* receptors: nicotinic/muscarinic cholinergic receptors
Autonomic transmitters
- Acetylcholine: acts on cholonergic receptors: nicotinic (iontropic) and muscarinic (g-protein coupled) receptors
- Noradrenaline: acts on adrenergic receptors: a and B receptors
What neurotransmitters do sympathetic/parasympathetic release over course of efference
Key flashcard
- preganglionic fibres for both release ACh which acts on nicotinic cholinergic receptors
- parasympathetic postganglionic fibres release ACh which acts on muscarine cholinergic receptors
- Sympathetic postganglionic fibres release noradrenaline which acts on a or B adrenergic receptors
Remember that ther are a couple of exeptions
Explain “special” part of the sympathetic nervous system
Fibre goes straight out of the spinal cord, through the sympathetic chain without synapsing, goes straight through the collateral/prevertebral ganglia again without synapsing and comes all the way out to its target: adrenal medulla gland that sits above the kidney. Finally synapses his here onto the post-ganglionic cell. But it doesn’t have an axon, and instead releases its neurotransmitter into the bloodstream which then acts as a hormone.
What do sympatheticd postganglionic cells of the adrenal medulla release
Adrenaline and noradrenaline into the blood: which act on a or B adrenergic receptors - hormonal component and often allows for whole body response!!!
List 3 complexities to the sympathetic/parasympathetic NS that don’t follow previous “rules”
- Sympathetic cholinergic fibres (due to length of pre/post ganglionic fibres) innervate sweat glands - expect post-G fibre to release norarenaline but instead, releases Ach
- Some postganglionic fibres use non-adrenergic non-cholinergic (NANC) transmitters (e.g. peptides)
- Sometimes co-released with the orthodox transmitter
Point 2 and 3 linked
In what 3 ways do somatic and autonomic efferent differ
(brief)
Tragets, axons, synapses
In what ways do sympathetic and parasympathetic efferent differ
(brief)
spinal outflow, location of ganglia, transmitters used, functions
Summarise the lengths of ganglia for the sypathetic and parasympathetic branches of the autonomic NS
- Sympathetic: short pre-ganglia, long post-ganglia fibres
- Parasympathetic: long pre-ganglia, short post-ganglia fibres
List features when sympathetic NS has taken over
- Airways dilate
- Heart beats faster
- Heart beats stronger
- Blood diverts to muscle
- Gut motility decreases
- Enzyme secretion in gut generally inhibited
- Stored energy is released
- Pupils dilate
- Eye focus far way
- Hair stands on end
- Mouth becomes dry
List features when parasympathetic NS has taken over
- Airways constrict
- Heart beats slower
- Heart beats weaker
- Blood diverts to gut
- Gut motility increases
- Enzyme secretion in gut generally stimulated
- Energy is stored
- Pupils constrict
- Eyes focus close up
- Hair lies flat
- Mouth starts drooling
What determines weather the sympathetic or parasympathetic NS is more “activated”
- Neurotransmitter released
- And receptor type that it acts on
Explain how the sympathetic/parasympathetic NS is more “activated” in terms of neurotransmitters and their receptors
- Acetylcholine: Cholinergic nicotinic (sympathetic) or muscarinin (parasympathetic) receptors
- Noradrenaline/adrenaline: a or B receptors (sympathetic)
ACh—>nicotinic receptors: S and P pre-ganglionic fibres
ACh —> P post-ganglionic fibres
Noradrenaline/Adrenaline—> S post-ganglionic fibres
